linux-kernel - [PATCH 25/26] x86/tdx: Warn about unexpected WBINVD

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Message-Id: <20211214150304.62613-26-kirill.shutemov@linux.intel.com>
Date:   Tue, 14 Dec 2021 18:03:03 +0300
From:   "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>
To:     tglx@...utronix.de, mingo@...hat.com, bp@...en8.de,
        dave.hansen@...el.com, luto@...nel.org, peterz@...radead.org
Cc:     sathyanarayanan.kuppuswamy@...ux.intel.com, aarcange@...hat.com,
        ak@...ux.intel.com, dan.j.williams@...el.com, david@...hat.com,
        hpa@...or.com, jgross@...e.com, jmattson@...gle.com,
        joro@...tes.org, jpoimboe@...hat.com, knsathya@...nel.org,
        pbonzini@...hat.com, sdeep@...are.com, seanjc@...gle.com,
        tony.luck@...el.com, vkuznets@...hat.com, wanpengli@...cent.com,
        x86@...nel.org, linux-kernel@...r.kernel.org,
        "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>
Subject: [PATCH 25/26] x86/tdx: Warn about unexpected WBINVD

WBINVD causes #VE in TDX guests. There's no reliable way to emulate it.
The kernel can ask for VMM assistance, but VMM is untrusted and can ignore
the request.

Fortunately, there is no use case for WBINVD inside TDX guests.

Warn about any unexpected WBINVD.

Signed-off-by: Kirill A. Shutemov <kirill.shutemov@...ux.intel.com>
---
 arch/x86/kernel/tdx.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/arch/x86/kernel/tdx.c b/arch/x86/kernel/tdx.c
index 2175336d1a2a..4da69bc760e1 100644
--- a/arch/x86/kernel/tdx.c
+++ b/arch/x86/kernel/tdx.c
@@ -521,6 +521,10 @@ static bool tdx_virt_exception_kernel(struct pt_regs *regs, struct ve_info *ve)
 	case EXIT_REASON_IO_INSTRUCTION:
 		ret = tdx_handle_io(regs, ve->exit_qual);
 		break;
+	case EXIT_REASON_WBINVD:
+		WARN_ONCE(1, "Unexpected WBINVD\n");
+		ret = true;
+		break;
 	default:
 		pr_warn("Unexpected #VE: %lld\n", ve->exit_reason);
 		break;
-- 
2.32.0